There was ~172,000,000 acres of fire annually prior to European colonization

Prior to European colonization most of the fires were located in the central and eastern regions, and were most common in the grassland ecosystems, where replacement fires could have happened every 1-3 years in those systems. The pine, oak and hickory forests of the east (especially the longleaf pine ecosystems of the southeast) would typically have surface fires every 5-10 years, with replacement fires being rare.

Out west where we see the most fires to day the forested ecosystems would have had fairly frequent fires. Those states had less fire overall due to the heterogeniety of ecosystems, that is most of those states have a mix of fire-dependant and fire-independant ecosystems.

Please note that ranges shift based on the fire type selected.

Fire severity varied by ecosystem type

Ecosystems have varying levels of different fire type (aka severity; surface, mixed or replacement). The map depicts historical locations of broad ecosystem groups.

Scroll down to explore how fire type varies for different ecosystem groups. Explore and note the patterns. For example, hover over the outer segment labeled “Replacement” then trace the bands to discover that most replacement fires occurred in the grassland ecosystems.

Continue scrolling to examine our broad vegetation groups today.

Increasing fire

It’s no surprise that the amount of fires occurring today is generally increasing. While far short of the ~172M acres that would have burned annually prior to European colonization, the amount of fire that is high-severity in ecosystems that would not had much of that fire type historically is increasing, and this number is not scaled to the current amount of natural vegetation.

Fire by state

This chart summarizes fire past (yellow dots) and present (green dots) for the lower 48 states.